pg_type

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pg_type

The pg_type system catalog table stores information about data types. Base
types (scalar types) are created with CREATE TYPE, and domains with
CREATE DOMAIN. A composite type is automatically created for each table in
the database, to represent the row structure of the table. It is also possible to create
composite types with CREATE TYPE AS.

Table 1. pg_catalog.pg_type

column

type

references

description

typname

name

Data type name.

typnamespace

oid

pg_namespace.oid

The OID of the namespace that contains this type.

typowner

oid

pg_authid.oid

Owner of the type.

typlen

int2

For a fixed-size type, typlen is the number of
bytes in the internal representation of the type. But for a variable-length type,
typlen is negative. -1 indicates a 'varlena' type
(one that has a length word), -2 indicates a null-terminated C
string.

typbyval

boolean

Determines whether internal routines pass a value of this type by
value or by reference. typbyval had better be false if
typlen is not 1, 2, or 4 (or 8 on machines where Datum is 8 bytes).
Variable-length types are always passed by reference. Note that
typbyval can be false even if the length would allow pass-by-value;
this is currently true for type float4, for example.

typtype

char

b for a base type, c for a
composite type, d for a domain, e for an enum
type, or p for a pseudo-type.

typisdefined

boolean

True if the type is defined, false if this is a placeholder entry
for a not-yet-defined type. When false, nothing except the type name, namespace, and
OID can be relied on.

typdelim

char

Character that separates two values of this type when parsing
array input. Note that the delimiter is associated with the array element data type,
not the array data type.

typrelid

oid

pg_class.oid

If this is a composite type, then this column points to the
pg_class entry that defines the corresponding table. (For a
free-standing composite type, the pg_class entry does not really
represent a table, but it is needed anyway for the type's
pg_attribute entries to link to.) Zero for non-composite
types.

typelem

oid

pg_type.oid

If not 0 then it identifies another row in
pg_type. The current type can then be subscripted like an array yielding values of
type typelem. A true array type is variable length
(typlen = -1), but some fixed-length
(tylpen > 0) types also have nonzero
typelem, for example name and
point. If a fixed-length type has a typelem then
its internal representation must be some number of values of the
typelem data type with no other data. Variable-length array types
have a header defined by the array subroutines.

typarray

oid

pg_type.oid

If not 0, identifies another row in pg_type,
which is the "true" array type having this type as its element. Use
pg_type.typarray to locate the array type associated with a
specific type.

typinput

regproc

pg_proc.oid

Input conversion function (text format).

typoutput

regproc

pg_proc.oid

Output conversion function (text format).

typreceive

regproc

pg_proc.oid

Input conversion function (binary format), or 0 if none.

typsend

regproc

pg_proc.oid

Output conversion function (binary format), or 0 if none.

typmodin

regproc

pg_proc.oid

Type modifier input function, or 0 if the type does not support
modifiers.

typmodout

regproc

pg_proc.oid

Type modifier output function, or 0 to use the standard
format.

typanalyze

regproc

pg_proc.oid

Custom ANALYZE function, or 0 to use the standard
function.

typalign

char

The alignment required when storing a value of this type. It
applies to storage on disk as well as most representations of the value inside
Greenplum Database. When multiple values are stored consecutively,
such as in the representation of a complete row on disk, padding is inserted before a
datum of this type so that it begins on the specified boundary. The alignment
reference is the beginning of the first datum in the sequence. Possible values are:

c = char alignment (no alignment
needed).

s = short alignment (2 bytes on most
machines).

i = int alignment (4 bytes on most
machines).

d = double alignment (8 bytes on many machines,
but not all).

typstorage

char

For varlena types (those with typlen = -1) tells
if the type is prepared for toasting and what the default strategy for attributes of
this type should be. Possible values are:

p: Value must always be
stored plain.

e: Value can be stored in a secondary relation
(if relation has one, see pg_class.reltoastrelid).

m: Value can be stored compressed
inline.

x: Value can be stored compressed inline or stored
in secondary storage.

Note that m columns can also be moved
out to secondary storage, but only as a last resort (e and
x columns are moved first).

typnotnull

boolean

Represents a not-null constraint on a type. Used for domains
only.

typbasetype

oid

pg_type.oid

Identifies the type that a domain is based on. Zero if this type
is not a domain.

typtypmod

int4

Domains use typtypmod to record the typmod to be applied to their
base type (-1 if base type does not use a typmod). -1 if this type is not a
domain.

typndims

int4

The number of array dimensions for a domain that is an array (if
typbasetype is an array type; the domain's typelem
will match the base type's typelem). Zero for types other than array
domains.

typdefaultbin

text

If not null, it is the nodeToString()
representation of a default expression for the type. This is only used for
domains.

typdefault

text

Null if the type has no associated default value. If not null,
typdefault must contain a human-readable version of the default expression represented
by typdefaultbin. If typdefaultbin is null and typdefault is not, then typdefault is
the external representation of the type's default value, which may be fed to the
type's input converter to produce a constant.